This invention relates to typographic apparatus and is more particularly directed to the provision of an electronic typographic apparatus, having a display panel preferably, for displaying a plurality of display lines. The invention incorporates the features of justification of one of the display lines and proportional spacing of the displayed characters.
In the past, many typographic devices have been developed, including such features as automatic justification, as well as the proportional display or characters. Such equipment, of an electromagnetic construction, is disclosed, for example, in co-pending U.S. application Ser. No. 212,895, now U.S. Pat. No. 3,945,480, filed Dec. 28, 1971, and U.S. application Ser. No. 213,045 now U.S. Pat. No. 3,993,179, also filed on December 28, 1971, these applications being assigned to the Assignee of the present invention.
At the present time, in view of significant advances that have been made in electronic components, it is natural to expect that electronic typographic devices may be fabricated that are more versatile, less cumbersome, and more easily produced than functionally equivalent mechanical and electromechanical devices. The present invention is therefore directed to the provision of electronic typographic apparatus embodying, insofar as practicable, the broader concepts disclosed in the above-mentioned applications. It will be apparent, of course, that direct application of all of the features of the disclosures of the above applications to electronic system would not necessarily result in the provision of a device of optimum design, and hence the present invention is directed to the adaptation of the systems of the above references to electronic equipment in such a manner that full advantage may be taken of the characteristics of available electronic components.
Briefly stated, in accordance with the present invention, a typographic apparatus is provided wherein coded data from a conventional keyboard is applied to a memory, which may be in the form of one or more shift registers. The device may be provided with an electronic display, such as a CRT display device, for the display of a plurality of lines of characters.
When the display has a plurality of display lines, each character memory corresponds to data of a given line of test, whereby under the control of control circuits, the corresponding test may be displayed at any of the display lines on the display device.
In a preferred embodiment of the invention, one of the display lines displays data that is currently being entered into the keyboard, and another of the display lines depicts a previously completed text line in justified form. In such an arrangement, since the display device is scanned continuously, counting circuits are provided in order to enable entry of newly received data in a position of the character memory corresponding to the data entry line, and at a position in the character memory corresponding to the data entry position of this line.
In the arrangement in accordance with the invention, the character memory corresponding to a display line at any given time is clocked at a rate determined by the desired width of each individual character. This is effected by applying the coded signals of the character memory continually to a programmed device, whereby each character may be assigned a determined width, and the character memory may thus be clocked at a rate such that the widths of the respective characters will be displayed.
In a further feature in accordance with the invention, correction is effected by backspacing operations which delete data previously stored in the character memory.
If a plurality of display lines are provided, and no text is displayed in the data entry line, operation of the backspace will cause a "roll down" placing data in the position of the data entry line for further backspacing and deletion operations. The print point is automatically set to the last character position of text line rolled down into the data entry line position.
In a further feature in accordance with the invention, justification is effected in one or more lines of the display by controlling the stepping rate of the corresponding character memory at determined times to increase the display width of word spaces. For this purpose, no modification of the character memory is required, but the amount and location of the necessary expansions of the word spaces may be stored in a further memory device.
In a particularly useful feature in accordance with the invention, means are provided for storing "fixed" spaces, which are not expanded in the manner of conventional word spaces, in a justification process. The provision of fixed spaces of this type readily enables an operator to position displayed characters in determined locations, to enable centered and flush right text.
The equipment in accordance with the invention is also capable of performing tabbing functions, wherein tabbing data is stored in a further memory.
In accordance with the concept of the present invention, the character memory thus stores only the data received from the keyboard, and the control for example for positioning the characters on the display is derived only at the instant the related character is to be displayed, on the basis of recognition of the character or function signal stored in the memory.
The typographic apparatus in accordance with the invention is readily adapted to operate in conjunction with a printer, for which purpose a suitable interface may be provided to adapt the signals derived in the device of the invention for control of the specific conventional printer employed.
The invention is particularly adaptable for the display of characters in a dot display matrix format, although other character formats may be employed if desired. The printing device need not be of the dot matrix type.